Hadrosaurids were a group of ornithopods also called the 'duck-bills' because of their broad, flattened toothless beaks. These dinosaurs were between 10 and 50ft long and lived in the Late Cretaceous period - the fossil evidence suggests that they were the last group of dinosaurs to evolve. Hadrosaurids were also the largest of the bird-footed, bird-hipped dinosaurs. Remains have been found in North and South America, Asia, and Europe. Hadrosaurs included Bactrosaurus, Hadrosaurus, Edmontosaurus, Brachylophosaurus and Lambeosaurus.

Bactrosaurus or 'Bactrian lizard' was a hadrosaurid dinosaur found in Mongolia. It lived in the Early Late Cretaceous period and was a small duck-billed dinosaur 13-20ft long. It may have been the ancestor of the other duck-billed dinosaurs. Bactrosaurus had a hadrosaurid-type flat head and high-spined vertebrae. It was a plant eating dinosaur that walked on its hind legs.

Hadrosaurus simply means 'big lizard'. Hadrosaurus was a large (26-33ft) duck-billed dinosaur with a toothless beak and rows of cheek teeth. It lived in the Late Cretaceous period and has been excavated in Alberta, Canada, as well as New Jersey, Montana and New Mexico. The New Jersey remains were discovered in 1858 and were at that time the most complete dinosaur skeleton in the world.

Lambeosaurus or 'Lambe's lizard' is named after Lawrence Lambe, an eminent Canadian paleontologist. Living in the Late Cretaceous period, remains of this crested duck-billed dinosaur have been excavated near Alberta, Canada; Montana, USA and Baja California, Mexico. Lambeosaurus was an herbivore with a toothless beak, rows of cheek teeth, and a square skull crest. It also had a backward pointing bony spike. This dinosaur was one of the biggest hadrosaurs, up to 50ft long.

Edmontosaurus means 'Edmonton lizard', and the remains of this dinosaur were found in the Late Cretaceous rock formation near Alberta, Canada. A hadrosaurid dinosaur also found in Montana and New Jersey, USA, Edmontosaurus was a large duck-billed dinosaur 32-42ft long, weighing 3-4 tons. It was a vegetarian with a spoon-shaped toothless beak and rows of grinding cheek teeth (numbering up to 1,000). A number of specimens have been found, suggesting that this was a common dinosaur of the Late Cretaceous period.

Brachylophosaurus or 'short-crested reptile' was a Late Cretaceous vegetarian hadrosaurid dinosaur, and remains have been found in Alberta, Canada; and Montana, USA. The first specimen was found in 1936 in Alberta. It was an early duck-billed dinosaur measuring 16-23ft long, with a bony crest on the top of its head.